Role of dobutamine stress echocardiography in heart transplant patients

A Comprehensive Excursus of the Roles of Echocardiography in Heart Transplantation Follow-Up

Current guidelines for the care of heart transplantation recipients recommend routine endomyocardial biopsy and invasive coronary angiography as the cornerstones in the surveillance for acute rejection (AR) and coronary allograft vasculopathy (CAV). Non-invasive tools, including coronary computed tomography angiography and cardiac magnetic resonance, have been introduced into guidelines without roles of their own as gold standards. These techniques also carry the risk of contrast-related kidney injury. There is a need to explore non-invasive approaches providing valuable information while minimizing risks and allowing their application independently of patient comorbidities. Echocardiographic examination can be performed at bedside, serially repeated, and does not carry the burden of contrast-related kidney injury and procedure-related risk. It provides comprehensive assessment of cardiac morphology and function. Advanced echocardiography techniques, including Doppler tissue imaging and strain imaging, may be sensitive tools for the detection of minor myocardial dysfunction, thus providing insight into early detection of AR and CAV. Stress echocardiography may offer a valuable tool in the detection of CAV, while the assessment of coronary flow reserve can unravel coronary microvascular impairment and add prognostic value to conventional stress echocardiography. The review highlights the role of Doppler echocardiography in heart transplantation follow-up, weighting advantages and limitations of the different techniques.

New Non-Invasive Imaging Technologies in Cardiac Transplant Follow-Up: Acquired Evidence and Future Options

Heart transplantation (HT) is the established treatment for end-stage heart failure, significantly enhancing patients' survival and quality of life. To ensure optimal outcomes, the routine monitoring of HT recipients is paramount. While existing guidelines offer guidance on a blend of invasive and non-invasive imaging techniques, certain aspects such as the timing of echocardiographic assessments and the role of echocardiography or cardiac magnetic resonance (CMR) as alternatives to serial endomyocardial biopsies (EMBs) for rejection monitoring are not specifically outlined in the guidelines. Furthermore, invasive coronary angiography (ICA) is still recommended as the gold-standard procedure, usually performed one year after surgery and every two years thereafter. This review focuses on recent advancements in non-invasive and contrast-saving imaging techniques that have been investigated for HT patients. The aim of the manuscript is to identify imaging modalities that may potentially replace or reduce the need for invasive procedures such as ICA and EMB, considering their respective advantages and disadvantages. We emphasize the transformative potential of non-invasive techniques in elevating patient care. Advanced echocardiography techniques, including strain imaging and tissue Doppler imaging, offer enhanced insights into cardiac function, while CMR, through its multi-parametric mapping techniques, such as T1 and T2 mapping, allows for the non-invasive assessment of inflammation and tissue characterization. Cardiac computed tomography (CCT), particularly with its ability to evaluate coronary artery disease and assess graft vasculopathy, emerges as an integral tool in the follow-up of HT patients. Recent studies have highlighted the potential of nuclear myocardial perfusion imaging, including myocardial blood flow quantification, as a non-invasive method for diagnosing and prognosticating CAV. These advanced imaging approaches hold promise in mitigating the need for invasive procedures like ICA and EMB when evaluating the benefits and limitations of each modality.

The risk of adverse events associated with atropine administration during dobutamine stress echocardiography in cardiac transplant patients: a 28-year single-center experience

BACKGROUND

Although dobutamine stress echocardiography (DSE) is performed in heart transplant patients, the safety profile of atropine administration in DSE in this setting is unclear.

METHODS AND RESULTS

We identified heart transplant patients who received atropine during DSE from January 1984 to August 2011 at our institution and compared them with a propensity-scored matched control group of heart transplant patients who underwent DSE without atropine. Adverse events were defined as significant arrhythmias (sinus arrest, Mobitz type II heart block, complete heart block, ventricular tachycardia, or ventricular fibrillation), hypotension requiring hospitalization, syncope or presyncope, myocardial infarction, and death. Forty-five heart transplant patients (median age 62 years, 82% male) received 0.2-1 mg atropine during DSE. Of these, 1 patient (2.2%) developed temporary complete heart block. No adverse events were identified in the control group of 154 patients who received dobutamine without atropine.

CONCLUSIONS

Our findings suggest that complete heart block can occur infrequently with the administration of atropine in heart transplant patients undergoing DSE. Therefore, patients should be appropriately monitored for these adverse events during and after DSE.

A prospective study of dobutamine stress echocardiography for the assessment of cardiac allograft vasculopathy in pediatric heart transplant recipients

Transplant CAV is the leading cause of graft loss beyond one yr post-heart transplant. Diagnosis can be challenging and the previous "gold standard," coronary ANG, tends to underestimate disease. The purpose of this study was to relate DSE to ANG for the diagnosis of CAV. Prospective annual DSE at a single centre on all heart transplant patients (1999-2006) were compared with results from routine coronary angiograms. Progression of CAV over time as determined by DSE and ANG and associated factors were sought through logistic regression models adjusted for repeated measures. There were 102 heart transplant patients (54 males) transplanted between 1989 and 2006. Median age at transplant was 17 months (0-16.6 yr). The initial DSE was at a median of 10-months post-transplantation. There was a high correlation between an abnormal DSE and an abnormality on ANG (p = 0.002). There was an increased probability of an abnormal DSE with increasing grade of CAV as assessed by ANG (p < 0.001). Factors associated with an abnormal DSE included older age at transplant (p = 0.04), higher grade of rejection (p = 0.002), higher total cholesterol (p = 0.04), higher LDL (p < 0.05), and older age at the time of DSE (p = 0.002). DSE result was not related to HDL, triglyceride or homocysteine levels, or to steroid or statin use. The probability of an abnormal DSE result increases with increasing angiographic grade of CAV, and thus DSE may be used for initial screening for CAV with ANG reserved for confirmation and grading. Patients transplanted at an older age and those with a greater history of rejection were at higher risk of a positive DSE and may require increased surveillance for CAV.

Dobutamine myocardial scintigraphy for the prediction of cardiac events after heart transplantation

BACKGROUND

The long-term outcome after heart transplantation (HTx) is essentially influenced by the occurrence and extent of cardiac allograft vasculopathy (CAV). Single photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) has been shown to be a useful and cost-effective non-invasive method in patients with known or suspected coronary artery disease, but its role in detecting CAV remains unclear.

AIM

To evaluate the accuracy and predictive value of dobutamine MPI in patients after HTx during a 12-month follow-up.

METHODS

Seventy-seven patients (60 males, 17 females) underwent a total of 216 dobutamine MPI examinations over a period of 5 years. Examinations were obtained an average of 89+/-42 months after orthotopic HTx according to a 1-day protocol using 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) with and without attenuation correction. For the present study, findings from 77 MPI examinations (one MPI examination per patient) were analysed visually and semiquantitatively using a 20-segment model. Summed stress scores (SSS) and summed rest scores (SRS) were calculated and receiver operating characteristic (ROC) analysis was performed to detect optimum threshold values. Patients were followed up for 12 months and cardiac events were registered.

RESULTS

Cardiac events were observed in 10 of the 77 patients. Good interobserver agreement was found for global visual and SRS-/SSS-based analysis (kappa=0.74 and 0.66, respectively). SSS was superior to SRS in the detection of cardiac events. ROC analysis showed an optimized SSS threshold value of three. For predicting a cardiac event during the 12-month follow-up, global visual and semiquantitative analysis reached sensitivities of 90% and 90%, specificities of 72% and 88%, accuracies of 74% and 87%, positive predictive values of 32% and 53% and negative predictive values of 98% and 98%, respectively. The sensitivity, specificity, accuracy and positive and negative predictive values for MPI to detect clinically relevant coronary artery stenoses (> or =50%) at conventional coronary angiography were 83%, 87%, 86%, 56% and 96%, respectively.

CONCLUSIONS

Non-invasive dobutamine MPI reliably identifies patients at risk for subsequent cardiac events in cases of CAV, with a high negative predictive value of 98% and an accuracy of 87%.

Non-invasive detection of coronary artery disease by dobutamine-stress echocardiography in children after heart transplantation

BACKGROUND

Coronary vasculopathy is the main cause of cardiac graft failure. Because yearly coronary angiography is invasive in children, a non-invasive method for detecting graft vasculopathy is needed. The aim of this study was to test dobutamine-stress echocardiography in a pediatric population to determine its feasibility, safety and reliability in the detection of graft coronary artery disease.

METHODS

Eighteen patients, aged 2 days to 16.8 years at transplantation (mean 8.4 years), underwent 44 dobutamine-stress echocardiography (DSE) exams, at a follow-up of 1.1 to 11.8 years (mean 5.1 years). Selective coronary angiography was performed for comparison. Echocardiographic recordings were obtained in 4 standard views of the left ventricle and measurements carried out within the frames of a 16-segment model. Segmental scores of contractility were obtained for each segment and a total segmental contractility index was calculated at each stage.

RESULTS

All patients reached the maximum dose stage. Maximum heart rate was 57% to 90% of predicted maximum. Maximum systolic blood pressure reached 190 mmHg. Segmental scores were normal in 37 and abnormal in 7 cases. Echographic results were concordant with angiography in 82% and discordant in 18% of the cases (4 negative DSEs with minor angiographic lesions, 2 positive DSEs with normal angiography), but there was no significant angiographic lesion with normal DSE.

CONCLUSIONS

DSE is a safe and highly feasible non-invasive technique in transplanted children. A normal DSE study successfully predicts the absence of significant coronary artery disease in the post-transplant population.

Prognostic value of contractile response during high-dose dipyridamole echocardiography test in heart transplant recipients

BACKGROUND

Coronary allograft vasculopathy (CAV) remains a main factor limiting long-term survival after heart transplantation (HTX). The diagnosis of CAV is still based on serial coronary angiography. In this study, we evaluated the prognostic value of high-dose dipyridamole echocardiography in HTX.

METHODS

Sixty-eight patients underwent dipyridamole echocardiography within 48 hours of their scheduled annual coronary angiography. Coronary allograft vasculopathy was defined as CAV 1 (focal or diffuse stenosis <50%) or CAV 2 (focal or diffuse stenosis >or=50%). Wall-motion score index (WMSI) was evaluated at rest and after dipyridamole administration.

RESULTS

Results of coronary angiography were normal in 43 patients (63%), showed CAV 1 in 11 (16%), and showed CAV 2 in 14 (21%). Rest wall motion was normal in 39 patients and abnormal in 29. After dipyridamole administration, wall motion remained normal in all 39 (Group 1, no CAV in 34 and CAV 1 in 5). Of 29 patients with rest wall-motion abnormalities, all reversed to normal after dipyridamole in 8 patients (Group 2, no CAV in 7 and CAV 1 in 1) and remained or worsened in 21 (Group 3, CAV 2 in 14 and no CAV or CAV 1 in 7). During follow-up (6 +/- 3 years), 15 patients had major cardiac events: 11 occurred in Group 3, whereas 4 occurred in Groups 1 and 2. Wall motion at rest and after dipyridamole administration and CAV were independent predictors for cardiac events; only dipyridamole WMSI >1 remained significant (p < 0.0001) at multivariate analysis.

CONCLUSIONS

Dipyridamole echocardiography is a simple, non-invasive test that after HTX may identify patients with altered wall motion who deserve stricter surveillance.

Relationship between dobutamine-induced regional wall motion abnormalities and coronary flow reserve in heart transplant patients without angiographic coronary artery disease

BACKGROUND

Regional wall motion abnormalities (RWMA) demonstrated by dobutamine stress echocardiography (DSE) are a sensitive predictor of coronary artery disease (CAD) in heart transplant recipients. However, RWMA have been shown to occur in patients with angiographically "normal" coronary arteries. The reasons for this are unknown. We sought to determine if abnormal responses to dobutamine in this setting can be explained by microvascular dysfunction in the coronary circulation as detected by decreased coronary flow reserve (CFR).

METHODS

Twenty-six consecutive heart transplant patients were evaluated prospectively. Five of 26 (19.2%) patients (seven coronary arteries) were excluded for poor acoustic windows on echocardiography. Another three patients were excluded for angiographically apparent CAD. CFR and wall motion score index (WMSI) derived from DSE were measured in the remaining 18 patients and formed the basis of this study. Patients were divided into two groups based on the absence (Group 1; n = 5) or presence (Group 2; n = 13) of RWMA on DSE. CFR was measured with the Doppler Flo-Wire in 34 coronary arteries (18 patients) and correlated with WMSI.

RESULTS

In Group 1 patients, CFR measured in eight coronary arteries was normal (2.6 +/- 0.4). In Group 2 patients, CFR measured in 26 coronary arteries also was normal (2.2 +/- 0.6; p = NS vs Group 1). In Group 2, CFR was measured in 20 of 24 vessels assigned to segments that developed RWMA. Only 6 of these 20 vessels (30%) had abnormal CFR. Overall, there was no correlation between decreased CFR and the presence of RWMA induced by dobutamine.

CONCLUSIONS

These data suggest that, in cardiac transplant patients with angiographically "normal" coronary arteries, inducible wall motion abnormalities during DSE cannot be attributed to coronary microvascular dysfunction as manifested by decreased CFR.

Prediction of mortality in heart transplant recipients by stress technetium-99m tetrofosmin myocardial perfusion imaging

Cardiac allograft vasculopathy is a major cause of mortality in heart transplant recipients. The aim of this study was to assess the prognostic value of stress myocardial perfusion imaging in heart transplant recipients. We studied 166 patients (age 54 +/- 10 years, 140 men) by symptom-limited bicycle exercise or dobutamine (up to 40 microg/kg/min) stress myocardial perfusion imaging 7.4 +/- 2.5 years after heart transplantation. An intravenous dose of 370 MBq of technetium-99m tetrofosmin was injected at peak stress and 24 hours after the stress test. An abnormal test was defined as reversible or fixed perfusion defects. Perfusion abnormalities were detected in 55 patients (33%). During a median follow-up of 2.5 years, 54 deaths (33%) occurred, 16 of which were due to cardiac causes. The incidence of perfusion abnormalities was higher in patients with subsequent cardiac death than in patients without subsequent cardiac death (69% vs 29%, p = 0.01). In an incremental multivariate Cox analysis, cardiac death was not predicted by age, gender, duration of transplantation, number of rejection episodes, or cytomegalovirus infection. In the next step, stress test parameters were added. The peak rate-pressure product was the only significant predictor at this step (risk ratio 0.84, 95% confidence interval 0.73 to 0.97, chi-square 7.7, p = 0.006). In the final step, the presence of abnormal myocardial perfusion was an independent predictor of cardiac death (risk ratio 3.5, 95% confidence interval 1.6 to 11.7, chi-square 4.7, incremental to clinical and stress test variables, p = 0.01). It is concluded that stress myocardial perfusion imaging with technetium-99m tetrofosmin single-photon emission computed tomography provides incremental data for the prediction of cardiac death in heart transplant recipients.

Modulation of catecholamine responsiveness and beta-adrenergic receptor/adenylyl cyclase pathway during cardiac allograft rejection1 2

BACKGROUND

This study investigated the changes of catecholamine responsiveness and beta-adrenergic receptor/adenylyl cyclase pathway during acute cardiac transplant rejection.

METHODS

Isogeneic Lewis to Lewis and allogeneic Dark Agouti (DA) to Lewis rat cardiac transplants were studied 3 and 5 days after heterotopic intraabdominal transplantation (n=6/group). Myocardial blood flow (MBF), left ventricular systolic pressure (LVSP), maximum pressure development (+dP/dt), and end-diastolic pressure (LVEDP) were measured using an intraventricular balloon. Contractile response to dobutamine (5 microg/kg/min) was also assessed. In separate groups beta-adrenergic receptor density and adenylyl cyclase activity were measured in the grafts, in the recipients' native hearts and in native hearts of sham-operated controls.

RESULTS

During mild to moderate rejection cardiac function indices remained unchanged, although MBF and contractile response to dobutamine decreased significantly (P<0.05) in the allogeneic group. The beta-adrenergic receptor density was significantly (P<0.05) increased in both isografts and allografts and in the native hearts of allografted recipients in comparison to native hearts of controls. Adenylyl cyclase activity showed a significant decrease (P<0.05) only in allografts. During severe rejection, LVSP and +dP/dt decreased and LVEDP increased in allografts in comparison to isografts (P<0.05). This was accompanied by a significant decrease in MBF, contractile response to dobutamine, beta-adrenergic receptor density, and adenylyl cyclase activity (P<0.05).

CONCLUSIONS

Both microcirculatory disturbances and primary alteration in adenylyl cyclase activity may contribute to decreased contractile reserve in mild to moderate cardiac allograft rejection, whereas beta-adrenergic receptor density seems to be also influenced by cardiac denervation. Severe rejection leads to systolic and diastolic heart failure with complex dysregulation of the beta-adrenergic receptor/adenylyl cyclase pathway and impaired microcirculation.

Impact of heart transplantation on the safety and feasibility of the dobutamine stress test

BACKGROUND

Dobutamine myocardial perfusion imaging is a useful method for evaluation of coronary artery disease. However, this technique does not allow for ischemia monitoring, which may have an impact on the safety of the test in heart transplant recipients due to cardiac sensory denervation. The aim of this study was to assess the impact of heart transplantation on the feasibility and complications of the dobutamine stress test.

METHODS

We studied 225 heart transplant recipients (mean age 57 +/- 7 years) and a control group of 225 patients without previous transplant matched for age and gender by dobutamine (up to 40 microg/kg per minute) stress myocardial perfusion imaging.

RESULTS

During the test, transplant recipients had a lower prevalence of premature ventricular contractions (23% vs. 37%, p < 0.001) and ventricular tachycardia (0.04% vs 7.5%, p < 0.0001) compared with control patients. By multivariate analysis, heart transplantation was a powerful independent variable associated with a reduced risk of ventricular arrhythmias (chi(2) = 20.8, p < 0.0001) and minor side effects (nausea, dizziness, anxiety, flushing, chills) (chi(2) = 20, p < 0.0001) during dobutamine stress. The target heart rate was reached in 82% of transplant recipients and in 77% of the control group. Overall feasibility (achievement of the target heart rate and/or an ischemic end-point) was 87% in the transplant and 86% in the control group.

CONCLUSIONS

Dobutamine stress myocardial perfusion imaging is a safe and feasible method for evaluation of coronary artery disease in heart transplant recipients. The prevalence of arrhythmias and minor complications using the dobutamine stress test is lower in heart transplant recipients compared with control patients. The independent association between heart transplantation and reduced risk of arrhythmias and minor side effects of the dobutamine stress test indicates that cardiac sensory and autonomic nerve function plays a major role in the induction of these complications during the test.

Coronary revascularization in heart transplant recipients by excimer laser angioplasty

BACKGROUND AND OBJECTIVE

Aggressive development of allograft coronary artery disease is a major cause of death in heart transplant recipients. Percutaneous balloon angioplasty is considered suboptimal for complex lesions in native coronary vessels and heart transplant recipients, alike. Excimer laser energy (308-nm wavelength) can successfully remove and vaporize atherosclerotic plaques in native coronary vessels; however, its application in heart transplant recipients has not been studied clinically yet.

STUDY DESIGN/MATERIALS AND METHODS

Six heart transplant recipients underwent percutaneous excimer laser (CVX-300, Spectranetics, Colorado Springs, CO) coronary angioplasty for treatment of a total of 10 discrete, obstructive coronary artery lesions. By using concentric or eccentric multifiber laser catheters, energy parameters were set at a fluence of 45 mJ/mm(2) or 60 mJ/mm(2) with a frequency of 25 Hz and 40 Hz, respectively, with a pulse duration of 135 ns and output of 200 mJ/pulse. The "saline flush" and "pulse and retreat" lasing techniques were used. In each case, adjunct balloon angioplasty was performed; in five lesions, an intracoronary stent was implanted. Angiographic evaluation was performed by visual assessment.

RESULTS

Each procedure was successful as defined by laser recanalization of the target lesion (reduction of target lesion stenosis in more than 20%) and subsequent adequate final luminal patency (reduction of target lesion stenosis to less than 50%) and absence of any major in-cardiac catheterization complication (such as perforation, acute closure, dissection, emergency coronary artery bypass surgery), or in-hospital complications (such as death, myocardial infarction, cardiac enzyme elevation, major bleeding), or need for surgical revascularization. A 92 +/- 5% preprocedural percent diameter stenosis was reduced by laser to 35 +/- 16% and by adjunct balloon angioplasty in all lesions and stenting in five lesions, to final residual stenosis of 2 +/- 6%. Angiographic follow-up between 2 and 6 months after the procedure demonstrated a target lesion restenosis rate of 22%.

CONCLUSION

Percutaneous excimer laser is safe and efficacious in the treatment of focal obstructive lesions caused by allograft coronary artery disease. These data represent an early clinical experience; thus, the long-term outcome of this revascularization method in recipients of heart transplantation will have to be determined by a large scale prospective, randomized, multicenter clinical study.

The role of stress echocardiography in children

Exercise and pharmacological stress echocardiography are well-accepted techniques of evaluating coronary artery disease in adults. In children, however, experience with stress echocardiography is limited and continues to evolve. The objective of this focused review was to describe the experience with exercise and dobutamine stress echocardiography in the pediatric population, with an emphasis on technique, current indications, and future directions. Experience is reported in children with prior Kawasaki disease or heart transplant recipients, as well as patients with congenital coronary abnormalities. In addition, stress echocardiography has been used in patients who have undergone coronary artery bypass graft surgery to evaluate short- and long-term graft patterning. Stress echocardiography appears to be a feasible, safe, and useful modality for the noninvasive assessment of flow-limiting stenosis in the pediatric population and can be used serially in the routine follow-up and risk stratification in children at risk for coronary events.

Diagnostic and prognostic use of stress echocardiography in stable patients

Stress echocardiography is an effective diagnostic and prognostic technique in stable patients with known or suspected coronary artery disease (CAD), myocardial infarction, or chronic left ventricular dysfunction and those undergoing noncardiac surgery. Stress echocardiography is sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events regardless of the clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Stress echocardiography provides incremental prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable to that from radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for one-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

The role of percutaneous transluminal coronary angioplasty in heart transplant recipients

OBJECTIVES

Review the acute and late results of percutaneous transluminal coronary angioplasty (PTCA) in heart transplant recipients and examine the factors predictive of restenosis.

BACKGROUND

Coronary graft disease (CGD) is the main factor responsible for late graft loss. Medical treatment, surgical revascularization, or retransplantation gives only suboptimal results in this regard. Therefore, PTCA has been attempted in this situation.

METHODS

More than 332 heart transplantations in our institution have been performed since 1992, the date of the first PTCA in our patients. We are currently in charge of 450 patients. All the characteristics, procedure-related information, and clinical outcome of patients needing PTCA were assessed by review of each patient's clinical records. All coronary angiograms were reviewed by an independent cardiologist.

RESULTS

Since 1992, 53 coronary sites have been dilated in the course of 39 procedures in 29 patients. Indication for PTCA was asymptomatic angiographic coronary graft disease in 35 sites (64.8%), angina in 9 (16.6%), silent ischemia in 2 (3.7%), acute myocardial infarction in 1 (1.8%), and CHF in 7 (12.9%). Primary success (< 50% residual stenosis) was obtained in 50 (94.3%) of 53 lesions. No periprocedural death occurred. Procedural complications were 1 transient acute renal failure and 1 persistent bleeding at the puncture site. Six months restenosis rate (defined as percent stenosis > 50%) was 32.5% (14/43). Mean follow-up was 1.27 year +/- 1.2 (SD). Five deaths (17. 2%) occurred in follow-up and were all in relation to coronary graft disease. Mean time separating PTCA from death was 0.9 year +/- 1.3 (SD). We also sought to look at factors predictive of restenosis. By multivariate analysis, a positive recipient's serology for cytomegalovirus (CMV) before the graft was the only factor found protective against restenosis (odds ratio 22.4; confidence interval 1.1 to 443.4).

CONCLUSION

PTCA in heart transplant recipients allows a high level of primary success with a low periprocedural-complication rate. Restenosis rate seems equivalent to restenosis rate in native coronary arteries. Mortality during follow-up is increased in this population and is the consequence of a high level of coronary events. Recipient positivity for CMV before the graft is associated with a protective effect from restenosis.

Accuracy of dobutamine tetrofosmin myocardial perfusion imaging for the noninvasive diagnosis of transplant coronary artery stenosis

BACKGROUND

Exercise stress myocardial perfusion scintigraphy has been used for the diagnosis of transplant coronary artery stenosis (TCAS) in cardiac allograft recipients. However, the role of pharmacologic stress myocardial perfusion imaging has not been evaluated. Aim of the study is to assess the accuracy of dobutamine stress 99m technetium tetrofosmin myocardial perfusion imaging for the diagnosis of TCAS in heart transplant recipients.

PATIENTS AND METHODS

We studied 50 patients (age 56 +/- 8 year, 45 men) at a mean of 6.4 +/- 2.8 years after cardiac transplant with dobutamine (up to 40 ìg/kg/min) stress 99m technetium tetrofosmin SPECT. Resting images were acquired 24 hours after the stress study. Significant TCAS was defined as > or =50% luminal diameter stenosis by coronary angiography.

RESULTS

Significant TCAS was detected in 30 patients (60%). Myocardial perfusion abnormalities (reversible and/or fixed defects) were detected in 27 of the 30 patients with and in 9 of the 20 patients without significant TCAS (sensitivity = 90%, CI 82-98, specificity = 55% CI 41-69, positive predictive value = 75%, CI 63-87, negative predictive value = 79%, CI 67-90 and accuracy = 76%, CI 64-88). Patients with multivessel TCAS had a larger stress perfusion defect score (5.6 +/- 3.1 vs 3.2 +/- 2.4, p < 0.05) compared to patients with single vessel TCAS. Among patients with abnormal perfusion who had no significant TCAS, 2 had lesions <50%, 2 had luminal irregularities and 5 had no abnormalities at angiography. Therefore specificity was 62% (8/13) in patients without any detectable angiographic abnormalities.

CONCLUSIONS

Dobutamine stress tetrofosmin myocardial perfusion imaging is a highly sensitive method for the detection of TCAS in recipients of cardiac allografts. The high negative predictive value of the test indicates that patients who demonstrate normal perfusion by this method may be excluded from further invasive studies.

Safety profile and hemodynamic responses to beta-adrenergic stimulation by dobutamine in heart transplant patients

STUDY OBJECTIVE

Dobutamine stress echocardiography (DSE) has been used as a screening tool for coronary artery disease after heart transplantation and in the identification of patients at risk for development of cardiac events. However, the safety profile of high-dose dobutamine in heart transplant patients has not been systematically examined. Accordingly, we studied the safety profile and hemodynamic responses to escalating doses of dobutamine to determine the influence of denervation.

DESIGN

We assessed the hemodynamic responses, heart rate (HR), and arterial BP indexes (mean arterial pressure, systolic BP [SBP], diastolic BP [DBP], and pulse pressure) to dobutamine in 87 heart transplant patients ([mean +/- SD] age, 51 +/- 1 years) and compared the results with 97 nontransplant patients (age, 63.0 +/- 1 years) who served as innervated control subjects.

MEASUREMENTS AND RESULTS

The baseline HR (84 +/- 2 vs 69 +/- 1 beats/minute, respectively; p < 0.001) and peak HR response (144 +/- 2 vs 117 +/- 2 beats/minute, respectively; p < 0.001) were significantly higher in heart transplant patients than in the nontransplant patients. SBP was lower in heart transplant patients than in nontransplant patients at baseline (131 +/- 2 vs 138 +/- 2 mm Hg, respectively; p < 0.02) and at peak (150 +/- 3 vs 158 +/- 3 mm Hg, respectively; p < 0.03). However, baseline DBP was higher in transplant patients than in nontransplant patients (86 +/- 1 vs 77 +/- 1 mm Hg, respectively; p < 0.001). The decrease in DBP was similar in both groups (15 mm Hg). The dose-response curve for HR was shifted leftward in heart transplant patients. Heart transplant patients attained a higher absolute HR at each infusion stage and higher rates of increase, but the decrease in DBP was not significantly different in the two groups.

CONCLUSIONS

These results show that there is augmented chronotropic response and expected decline in DBP in response to dobutamine infusion in heart transplant patients. This increase in myocardial oxygen demand and a decrease in coronary perfusion pressure may be important mechanisms in the development of ischemic abnormalities that are detectable as regional dysynergy on echocardiography.

Diagnostic and Prognostic Use of Stress Echocardiography and Radionuclide Scintigraphy

Stress echocardiography and radionuclide scintigraphy are effective diagnostic and prognostic techniques in patients with known or suspected coronary artery disease (CAD), myocardial infarction (MI), chronic left ventricular dysfunction (LVD), and those undergoing noncardiac surgery. Both are sensitive and specific for the detection and extent of CAD. Negative tests confer a high negative predictive value for cardiac events irrespective of clinical risk. Positive studies confer a high positive predictive value for ischemic events in patients with intermediate to high clinical risk. Both provide incremental diagnostic and prognostic information relative to clinical, resting echocardiographic, and angiographic data. Meta-analysis studies have shown that the diagnostic and prognostic information provided by stress echocardiography is comparable with radionuclide scintigraphic stress tests. Stress echocardiography may be more specific for the detection and extent of CAD, whereas radionuclide scintigraphy may be more sensitive for single-vessel disease. Sensitivities are similar for the detection and extent of disease in patients with multivessel CAD.

Dobutamine stress echocardiography: experience in pediatric heart transplant recipients

BACKGROUND

Transplant coronary arteriopathy causes late death and is difficult to detect noninvasively. Dobutamine stress echocardiography is being used for risk stratification in adult recipients at some transplant centers, thus we investigated its role in a pediatric population.

METHODS

We performed 46 stress echo studies (mean age = 11.8 years; mean years post transplantation = 4.3). An atropine/dobutamine protocol (5-40 mcg/kg/min) was used to attain a predicted target heart rate. Serial echocardiographic images were acquired at baseline and at each increment of dobutamine and recovery, and were digitized online. Data were correlated with endomyocardial biopsy (n = 23), coronary angiography (n = 26) or autopsy (n = 6). All studies were well tolerated.

RESULTS

Target heart rate was achieved in 41/46 (89%) studies. The mean heart rate significantly increased from 95 to 169 beats/min and mean systolic blood pressure from 123 to 153 mm Hg (p<.05). The mean peak pressure-rate product was 23,041 beats-mm Hg/min. Coronary arteriopathy was confirmed in 5 patients by angiography (n = 3) explanted heart (n = 1) or autopsy (n = 4). In this group, abnormalities included a new reversible wall motion abnormality (n = 2), left ventricular cavity dilation with stress (n = 3), ischemia (n = 2), increased mitral insufficiency (n = 1) and marked diastolic dysfunction (n = 1). A positive study predicted death or graft failure (p< .0005).

CONCLUSIONS

Echocardiographic abnormalities during stress correlated with coronary arteriopathy in this small cohort of patients; however, larger multi-center studies are warranted to assess the utility of dobutamine stress echocardiography for risk stratification for coronary disease in pediatric transplant recipients.